Syed Sakhawat Shah

Redox Behavior of Anticancer Chalcone on a Glassy Carbon Electrode and Evaluation of its Interaction Parameters with DNA

The interaction of anticancer chalcone [AMC, 1-(4′-aminophenyl)-3-(4-N,N-dimethylphenyl)-2-propen-1-one] with DNA has been explored using electrochemical, spectroscopic and viscometric techniques. A shift in peak potential and decrease in peak current were observed in cyclic voltammetry and hypochromism accompanied with bathochromic shift were noticed in UV-Vis absorption spectroscopy. These findings were taken as evidence for AMC –DNA intercalation. A binding constant (K) with a value of 6.15 × 105 M−1 was obtained from CV data, which was also confirmed by UV-Vis absorption titration. Moreover, the diffusion coefficient of the drug with and without DNA (Db and Du), heterogeneous electron transfer rate constant (ko) and electron affinity (A) were also calculated from electrochemical data.

Effect of sonication conditions: solvent, time, temperature and reactor type on the preparation of micron sized vermiculite particles.

The effects of temperature, time, solvent and sonication conditions under air and Argon are described for the preparation of micron and sub-micron sized vermiculite particles in a double-jacketed Rosett-type or cylindrical reactor. The resulting materials were characterized via X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area analysis, chemical analysis (elemental analysis), Thermogravimetry analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5h of sonication, whereas longer times promoted aggregation again. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures according to physical/chemical properties of the used solvent. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction [001]; but structural changes were not observed. Sonication at different conditions also led to surface modifications of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicated clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type.

Separation and recycling of nanoparticles using cloud point extraction with non-ionic surfactant mixtures

A viable cost-effective approach employing mixtures of non-ionic surfactants Triton X-114/Triton X-100 (TX-114/TX-100), and subsequent cloud point extraction (CPE), has been utilized to concentrate and recycle inorganic nanoparticles (NPs) in aqueous media. Gold Au- and palladium Pd-NPs have been pre-synthesized in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, then dispersed in aqueous non-ionic surfactant mixtures. Heating the NP-micellar systems induced cloud point phase separations, resulting in concentration of the NPs in lower phases after the transition. For the Au-NPs UV/vis absorption has been used to quantify the recovery and recycle efficiency after five repeated CPE cycles. Transmission electron microscopy (TEM) was used to investigate NP size, shape, and stability. The results showed that NPs are preserved after the recovery processes, but highlight a potential limitation, in that further particle growth can occur in the condensed phases.

A UV-Visible Study of Partitioning of Pyrene in an Anionic Surfactant Sodium Dodecyl Sulfate

The interaction of hydrophobic dye pyrene with sodium dodecyl sulphate (SDS), an anionic surfactant, was studied in the process of solubilization. Difference UV-Visible spectroscopy was used to carry out the study. The partition coefficient (Kx), and number of dye molecules incorporated per micelle (n) was calculated. High Kx value shows that pyrene is partitioned strongly from polar to nonpolar environment. Steady-state fluorescence spectroscopy is used to check the environment of the pyrene as it is a well-known fluorescent probe. Onset of slope in curves is used to determine the critical micelle concentration (CMC).

Microemulsion System with Improved Loading of Piroxicam: A Study of Microstructure

Formulation of a new oil-in-water (o/w) microemulsion composed of castor oil/Tween 80/ethanol/phosphate buffer for enhancing the loading capacity of an anti-inflammatory drug piroxicam has been accomplished. The pseudo-ternary phase diagram has been delineated at constant surfactant/cosurfactant ratio (1:2). The internal structure of so created four-component system was elucidated by means of an analysis of isotropic area magnitudes in the phase diagram. Conductivity (σ), kinematic viscosity (kη), and surface tension (γ) studies with the variation in Φw (weight fraction of aqueous phase) show the occurrence of structural changes from water-in-oil (w/o) microemulsion to oil-in-water (o/w). Along with the solubility and partition studies of piroxicam in microemulsion components, the changes in the microstructure of the microemulsion after incorporation of drug have been evaluated using pH, σ, γ, kη, and density studies. Piroxicam, a poorly water-soluble drug displayed high solubility (1.0%) in an optimum microemulsion formulation using ethanol (55.0%), Tween 80 (26.5%), castor oil (7.5%), and phosphate buffer (11.0%). The results have shown that the microemulsion remained stable after the incorporation of piroxicam. Fluorescence spectra analysis taking pyrene as fluorescent probe was performed, and the results showed that pyrene was completely solubilized in the oil phases of the bicontinuous microemulsions. The fluorescence spectrum of the model drug piroxicam was used to probe the intramicellar region of nonionic microemulsion. The results showed that the piroxicam was localized in the interfacial film of microemulsion systems more deeply in the palisade layer with ethanol as the cosurfactant.

A spectroscopic study of hemicyanine dyes in anionic micellar solutions

The interaction of amphiphilic hemicyanine dyes i.e. (dialkylamino)stilbazolium butyl sulphonate (R = −CH3 to −C5H11) with sodium dodecyl sulphate (SDS), an anionic surfactant, in the process of solubilization was studied by absorption spectra as a function of surfactant concentrations above and below critical micelle concentration. Absorption spectra showed a red shift for dyes with small dialkyl chains and a blue shift for dyes with long dialkyl chains. Electronic transition energies (ΔET) and the approximate number of dye molecules incorporated per micelle were estimated at particular surfactant concentrations. Hydrophobic-hydrophilic force balance plays an important role in the process of solubilization of dyes in aqueous micellar solution.

THERMODYNAMIC CHARACTERIZATION OF DEXAMETHASONE SODIUM PHOSPHATE AND ITS COMPLEX WITH DNA AS STUDIED BY CONDUCTOMETRIC AND SPECTROSCOPIC TECHNIQUES

Electrical conductivities were measured to calculate critical aggregation concentration (cac) of dexamethasone sodium phosphate (DSP) at various temperature from 298-313K with an increment of 5 K and in this way its thermodynamic parameters like Gibbs energy of aggregation ( ° ∆ agg G ) , enthalpy of aggregation ( ° ∆ agg H ) and entropy of aggregation ( ° ∆ agg S ) were estimated. The results demonstrate that DSP forms enthalpy driven aggregates through open association process. Furthermore, its interaction with DNA was studied by UV-Vis spectroscopy. The binding constant of DSP-DNA interaction was evaluated at 298 K and

Thermodynamic dissociation constants of benzoic and nitrobenzoic acids in mixtures of ethanol and 1-propanol with water at 25°C

The molar conductances of dilute solutions of benzoic and 2-, 3-, and 4-nitrobenzoic acids in binary mixtures of ethanol and 1-propanol with water have been measured at 25°C. The data were fitted to the Lee- Wheaton conductance equation for the derivation of thermodynamic dissociation constants and limiting molar conductances. The results were compared with those in literature pertaining to analogous media and with those already found in methanol-water mixtutes. The findings are interpreted in terms of solute- solvent interactions, intramolecular hydrogen bonding, resonance, the inductive effect and the substituent position. The study showed that the dissociation order decreases as 2-nitrobenzoic acid >3-nitrobenzoic acid ≈4-nitrobenzoic acid > benzoic acid, in all three types of alcohol-water mixtures.

Synthesis of Novel Fluorescent Cyclohexenone Derivatives and their Partitioning Study in Ionic Micellar Media

An approach is demonstrated toward the synthesis of four novel cyclohexenone derivatives (CDs) via a convenient route of Michael addition of ethyl acetoacetate. The molecular structures of CDs were confirmed by means of FT-IR, 1H NMR, EIMS, UV and also by X-ray single crystal structure analysis. CDs are strongly fluorescent compounds and their fluorescent spectra exhibits intense violet fluorescence. To model the binding to biological membranes the behavior of CDs in micellar solutions of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic surfactant, sodium dodecylsulfate (SDS) has also been examined. The characteristics of partition and binding interactions of CDs with CTAB and SDS were investigated by UV-Visible and fluorescence spectroscopic techniques. Higher values of all mentioned interactions in case of CTAB, compared to SDS, indicate that there are greater interactions between the CDs and CTAB than with SDS.

Separating nanoparticles from microemulsions.

Water-in-oil microemulsions (w/o μEs) stabilized by the cationic surfactant cetyltrimethylammonium chloride (CTACl) have been used as reaction media to generate Au nanoparticles (Au-NPs). In addition the pure μEs have been used as media to disperse Au and Pd-NPs, which have been pre-synthesised in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, and also commercially available SiO(2)-NPs. A general method for recovery and separation of the nanoparticles from these mixed NP-μE systems has been demonstrated by tuning phase behavior of the background microemulsions. Addition of appropriate aliquots of water drives a clean liquid-liquid phase transition, resulting in two macroscopic layers, the NPs preferentially partition into an upper oil-rich phase and are separated from excess surfactant which resides in a lower aqueous portion. UV-vis and (1)H NMR spectroscopy have been used to follow these separation processes and quantify the recovery and recycle efficiencies for the different NPs. For example, ∼90% of the microemulsion-prepared Au-NPs can be recovered; with even greater separation efficiencies attainable for pre-synthesised MES-stabilized Au-MES-NPs (∼98%) and Pd-MES-NPs (92%). For the silica NP-μE dispersions gravimetry indicates ∼84% recovery of the NPs. TEM images of all systems showed that NP shapes and size distributions were generally preserved after these phase transfer processes. This low-energy and cost-effective purification route appears to be a quite general approach for processing different inorganic NPs, having advantages of being isothermal, using only commercially available inexpensive components and requiring no additional organic solvents.